With the development of industrial technologies, materials are required to have various characteristics, thereby making it difficult to satisfy required characteristics only with inherent properties of the materials. For this reason, demand for composite materials is gradually increasing.
Copper and aluminum have been widely used for heat exchangers or heat sinks, and in recent years, heat dissipation materials are required to have light weight, high strength, and higher thermal conductivity on account of high energy density caused by high functionality and efficiency of devices.
Aluminum, which is a lightweight material, has attracted a lot of attention as a heat dissipation material and is inevitably alloyed to achieve proper mechanical properties for heat dissipation materials. Alloying of aluminum may degrade thermal and electric conductivity in spite of enhancement of machinability and mechanical properties of aluminum materials.
Accordingly, in order to improve thermal and electrical conductivity as well as mechanical properties, there have emerged technologies for combining aluminum with nano-materials, such as carbon nanotubes, exhibiting better thermal and electric properties than aluminum, thereby utilizing thermal and electric properties of nano-materials and improving mechanical properties of structural materials through dispersion strengthening, instead of typical metallurgical methods.
Powder metallurgy has been widely used to produce composite materials and has also achieved some results in compositeness of carbon nanotubes. However, powder metallurgy is inadequate to respond to increasing demands for composite materials in terms of economic feasibility and scale-up. Therefore, a lot of attention is being focused on composite technologies using casting.
In the production of carbon nanotube-aluminum composite materials through typical casting, a problem of dipping carbon nanotubes, which are dispersion particles, into molten aluminum, which is a dispersion medium, has to be solved first. However, the dispersion particles have a lower specific gravity than the dispersion medium in the carbon nanotube-aluminum composite materials, and thus the dispersion particles are difficult to dip into the dispersion medium due to buoyant force.
The present invention relates to a technology for production of composite materials, such as carbon nanotube-aluminum composite materials, in which dispersion particles are lighter than a dispersion medium.
The background technique of the present invention is disclosed in Korean Patent Publication No. 10-2010-0008733 (published on Jan. 26, 2010 and entitled “Heat sink with composite material having covalently bonded carbon nanotube”).